Field of the Invention
The present invention relates to a fuel injection device including fuel injectors for use in a combustor of a gas turbine engine.
Description of Related Art
In recent years, in consideration of the environment, there is a need for a reduction of emissions such as NOx (nitrogen oxide) emitted from gas turbine engines. As a fuel injection device for the conventional aircraft gas turbine combustor, a fuel injection device of a diffusive combustion type is generally known. In the diffusion combustion type, since the burning reaction takes place based on the stoichiometric mixture ratio, the flame temperature tends to increase. Considering that the emission of NOx is known to exponentially increase with the increase of the flame temperature, lowering of the flame temperature appears to effectively suppress the emission of NOx. However, in the current situation of the propensity for high temperature and high pressure in the gas turbine engine, further suppression of the emission of NOx with the conventional diffusive combustion method is limited.
In order to lower the flame temperature, a fuel injection device of a lean combustion method is considered effective. The lean combustion method is known to be a method of burning an air-fuel mixture in which the ratio of fuel relative to air is lowered. The lean combustion according to this method contributes to a considerable reduction of the flame temperature as compared with that afforded by the conventional diffusive combustion method. On the other hand, however, the lean combustion method tends to result in an instable and incomplete combustion because of the relatively low flame temperature. In view of this, a concentric-type fuel injection device in which a pilot fuel injector is disposed on an inner side and a main fuel injector is disposed on an outer side so as to be concentric with the pilot fuel injector is used (see, for example, Patent Document 1). This concentric-type fuel injection device realizes a low NOx emission by mainly causing the main fuel injector to perform lean combustion while causing the pilot fuel injector to maintain stable combustion by a diffusion combustion method during a high power operation, and by causing the pilot fuel injector to stabilize a flame by diffusion combustion during a low power operation.